1. Field of the Invention
This invention relates to a procedure for the unblocking and the removal of the protection film of a lens during its manufacturing process
2. Description of the Related Art
The manufacturing process of lenses aimed for glasses and optics in general includes the machining and polishing of a block or crystal or an optical material and subsequently a surface treatment through the application of chemical coatings among some other steps.
In this machining procedure, the block of crystal or the optical material have a protection layer on its front side in order to avoid any fortuitous scratching, involving the machining of the back side of a block of crystal and the cutting of the contour according with the shape of the attachment rim required by the glasses.
In order to hold firmly the block of crystal during the machining process, a support is adhered to the said block of crystal using an alloy layer or a low temperature melting material having a great surface tension that is the responsible for the adhesion.
This joining together the support and the block of crystal is carried out on the side where the protection plastic film is located. The support may be suitable for fitting using an intermediate duct in the crystal machining machine.
Once the lens has been machined from the block, the support and the protection film must be removed in order to proceed to carry out the surface chemical treatments and finishing process. For this, the support is removed by a knock or impact to weaken the surface tension that holds the melting alloy. This process implies a high risk of breaking the fragile machined lens thus a high rejection of material can happen due to deterioration.
Besides, to remove the protection layer, a blade or similar element is used to scrape the contour of the lens in order to lift the protection film and achieve a safe removal. This is a trick operation because during the machining and cutting processes of the lens, the film is adjusted to the contour of the said lens thus the process of scratching and lifting the protection film can cause small scratches and damages in the edge of the lens thus altering its quality. Besides, this operation must be performed manually.
This operation of unblocking the support and removing the protection film is usually carried out for a set of two lenses because the most common way is to carry out the machining with a two-lense set required for one pair of glasses.